1. Field of the Invention
This invention relates to an image processing method, an image processing program, an image processing apparatus, and a digital still camera using the image processing apparatus.
2. Description of the Related Art
With an image input unit, such as a digital still camera (simply, digital camera) using image input means of CCD, etc., the image input means may output not only an electric signal responsive to the amount of received light, but also an unnecessary electric signal. This unnecessary electric signal is contained in electronic data output from pixels making up an image as noise.
Hitherto, to remove noise contained in an image, edges contained in the image have been detected from the output electronic data and information concerning the detected edges has been used to determine the smoothing range for performing image processing of noise removal, etc. For example, using information concerning the detected edges, in the proximity of each edge, smoothing has been performed in a narrow range along the edge and in the surroundings of remote pixels from the edge, smoothing has been performed in a wide range.
To detect an edge, generally, output values of electronic data output from the pixels making up a matrix centering on a pixel of interest (for example, matrix of 3×3 pixels, 5×5 pixels, etc.,) are used. The electronic data output from the pixels of the image input means is separated into a brightness component and a color difference component when image processing is performed. To detect an edge as described above, the brightness component separated from the electronic data is used.
To use the brightness component to detect an edge, if the image is an image with large change in brightness component for each pixel like an image of photographing a landscape or a portrait, for example, an edge can be detected effectively.
However, for an image with small brightness change, but with large hue change like an image of photographing a picture pattern printed on clothing, for example, if the brightness component is used for detecting an edge, it is feared that the edge which should be actually contained in the image may not be detected.
That is, in the image processing method in the related art using only the brightness component, if an edge of the brightness component is not contained in and an edge of the color difference component is contained in the pixel of interest, no edge may be detected. Consequently, smoothing is also performed in the surroundings of the edge and there is a fear of incurring breaking of the image.
The number of pixels of the electronic data output from the image input means depends on the number of pixels of the image input means. Thus, to form an image having a larger number of pixels than that of the electronic data output from the image input means, pixels need to be interpolated.